The present invention relates generally to synthetic filaments and to their processes and systems for manufacture. More specifically, the present invention relates to processes and systems for making melt-spun, synthetic polymeric yarns of bulked continuous filaments (BCF).
I. Definitions
As used herein, certain terms have the following meanings:
xe2x80x9cFilamentxe2x80x9d or xe2x80x9cfilamentsxe2x80x9d mean fibrous strands of extreme or indefinite length. In contrast, xe2x80x9cstaple fibersxe2x80x9d mean fibrous strands of definite and short lengths.
xe2x80x9cYarnxe2x80x9d means a collection of numerous filaments which may or may not be entangled, twisted or laid together.
xe2x80x9cOne-stepxe2x80x9d means a process for making yarn where the yarn is not wound-up between spinning, drawing and texturing.
xe2x80x9cTexturingxe2x80x9d means any operation on filaments which results in crimping, looping or otherwise modifying such filaments to increase cover, resilience, bulk or to provide a different surface texture or hand. A xe2x80x9cbulked continuous filamentxe2x80x9d is therefore a xe2x80x9cfilamentxe2x80x9d which has been subjected to one or more xe2x80x9ctexturingxe2x80x9d operation(s).
II. Background of the Invention
One-step processes for manufacturing melt-spun polymeric yarns of bulked continuous filaments (BCF) are known as evidenced by the following U.S. Pat. Nos.: 5,804,115; 5,487,860; 4,096,226; 4,522,774; and 3,781,949 (the entire content of each cited U.S. Patent being incorporated expressly hereinto by reference). In general, such processes involve the continuous sequential operations (i.e., without any intermediate winding of the yarn) of spinning, drawing and texturing. The resulting BCF yarn is thereafter wound on a package either sold as is or subjected to further processing (e.g., coloration, entangling with other yarns, fabric formation, and the like).
Conventional one-step BCF yarn production techniques typically involve the melt-spinning of multiple polymeric filament streams which, when cooled form the precursor (or undrawn) filaments of the later BCF yarn. These undrawn filaments are then typically immediately directed to separated pairs of godet rolls (sometimes referred to as xe2x80x9cduosxe2x80x9d in art parlance) operating at different rotational speeds. The BCF yarn will therefore be drawn between such duos at a desired draw ratio dependent on the duo speed differential, yarn temperature, yarn speed and the like. The duos are typically heated to the same temperature in order to elevate the filament temperature prior to texturing.
The thus drawn and heated yarn is then subjected to a texturing operation, usually accomplished by feeding the drawn continuous filament yarn into a fluid jet texturing unit at a rate faster than the rate at which the textured yarn is drawn off and subjecting the yarn in the unit to a turbulent region of a fluid jet, usually at elevated temperature (e.g., a so-called fluid jet texturing method). The resulting textured continuous filament yarn exhibits increased bulk as compared to the non-textured yarn being fed into the texturing unit to achieve the BCF yarn which may then be wound up to form a yarn package.
III. Summary of the Invention
Broadly, the present invention is embodied in processes and apparatus whereby the morphology of BCF yarns can be variably controlled. More specifically, according to the present invention, the BCF yarn is melt-spun, drawn and textured, wherein prior to texturing, the yarn is subjected to differential temperature condition. Most preferably, such differential temperature condition is accomplished using the duo rolls employed in drawing the BCF, such that one of the rolls is maintained at a greater temperature as compared to the other of the rolls. Most preferably, it is the upstream-most roll (relative to the general conveyance path of the filament toward the texturing unit) which is the hotter of the duo rolls.
These and other aspects and advantages will become more apparent after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.